As shown in FIG. 1, the existing process when establishing a connection in a multilayer network is as follows:
(1) after an intermediate node receives path message, it judges whether it is located on the area boundary of a Label Switch Path (LSP) or not according to explicit route object (ERO) carried in the path message and the locally saved route database information.
(2) if it is located on the area boundary, it also needs to determine another boundary node in this area according to the ERO and the route database information.
(3) according to the two determined boundary nodes, the low-layer network route information located between the two boundary nodes is extracted from the ERO.
(4) the first node on the area boundary triggers a low-layer network signaling to establish a new forwarding adjacency LSP (FA-LSP) so as to form a Forwarding Adjacency (FA) relationship between the area boundary nodes. Alternatively, the already existing forwarding adjacency relationship located between the area boundary nodes can be used, without the need of triggering the low-layer network signaling.
(5) After there exists the forwarding adjacency relationship between the area boundary nodes, the process of establishing the signaling in this layer continues.
In accordance with the prior art, in the case of no cooperation with the virtual network topology manager (VNTM) or no configuration of the appropriate strategy, the area boundary node must determine the area boundary based on the route database saved by it and the ERO object carried in the signaling and according to the algorithm provided in the standard RFC4206.
There are some foreseeable scenarios: traffic engineering databases (known as TED or the IGP database) are centralized to be managed, for example, the route database only exists in a node running the Path Computation Element (PCE), other nodes do not have route databases. Therefore if an intermediate node does not have a route database, it is not able to determine the area boundary in the process of sending the signaling.